1. Field of Invention
The present invention relates to an adaptive phase-shifted synchronization clock generation circuit and a method for generating phase-shifted synchronization clock, in particular to one that automatically detects the number of circuit modules to adaptively determine a phase difference.
2. Description of Related Art
Please refer to FIG. 1, wherein multiple switching circuit modules PWM[1]-PWM[N] receive the same input voltage Vin. If every circuit module has the same clock phase, that is, the power switches in all the circuit modules are conducted at the same time, a large ripple would be generated at the input side, as shown in FIG. 2. And a capacitor Cin with a large capacitance is required to eliminate the coupling effect caused by the large ripple. As shown in FIG. 3, if the clock phases of the switching circuit modules are shifted from one another, the ripple effect at the input side can be alleviated. The switching circuit modules may be, for example, switching power regulators which convert the voltage Vin into respective output voltages (Vo[1]-Vo[N]), or may be other circuits controlled by pulse-width modulation (PWM) signals. A similar problem may also occur when multiple switching power regulators provide power to the same output node.
U.S. Pat. Nos. 7,259,687; 7,493,504; and 7,504,895 propose methods of shifting clock phases, but they cannot automatically determine the phase difference between two circuit modules according to the total number of circuit modules in a circuit. These prior art patents can provide only a fixed phase difference (such as 90° or 180°) between two circuit modules, or they require an external setting to determine the phase difference. For example, U.S. Pat. No. 7,259,687 discloses the structure as shown in FIG. 4, wherein whenever a circuit module is inserted, a resistor R has to be connected correspondingly; in other words, this prior art sets the phase difference between circuit modules according to the number of the connected resistors. However, from the viewpoint of a circuit board manufacturer, because the number of the circuit modules to be actually mounted is unknown, the number of the resistors cannot be determined in advance, and therefore it lacks flexibility in production. Alternatively, if the resistors are not provided in advance on the circuit board, it would be inconvenient for a user because the user has to connect the resistors by himself at the time of actual use.
In view of such drawback, the present invention proposes an adaptive phase-shifted synchronization clock generation circuit and a method for generating phase-shifted synchronization clock, wherein the phase difference can be automatically and adaptively determined without manual setting.